"You just think to yourself, 'There's no way this guy is gonna live up to his reputation.' And then he does and it's like, 'What?! Really?!'" Watson marveled. "He's funny and kind and generous to work with and very hard working and he's all the things. He is all the things."

The Circle follows a young tech genius named Mae Holland (Watson) who gets hired to work for the world's leading social media and software company. As she quickly rises through the ranks, the company's founder, Eamon Bailey (Hanks), begins to mentor her, and introduces her to a massive experiment the company is undertaking that could forever change the boundaries of privacy and freedom.

In the tense drama -- directed by James Ponsoldt and based off the best-selling Dave Eggers novel of the same name -- Hanks plays a morally dubious and ethically questionable character, which is something of a departure for the star, who typically headlines films as the unfalteringly likable hero.

According to Watson, that tonal shift is "what is so amazing about his performance."

"There’s something so unexpected about it," Watson said. "He's like, all likeness and love and light on the outside, but there's something else [inside]."

"It was wonderful working with him," she shared. "It was a really personal relationship for me, so it’s not something I feel comfortable talking about… but he was wonderful."

Given the subject matter of her new paranoia-driven drama -- specifically the total loss of privacy in the digital age -- Watson said she began to think differently about her social media presence as a result of working on the film.

"I remember reading the book and I like, I couldn't sleep," she recalled. "I was thinking about it for weeks."